He was expected to meet with the nation's president following the cabinet meeting, according to the prime minister's office. Greece's main opposition leader Antonis Samaras said early Thursday that he is prepared to enter a coalition government as an interim stage leading to new elections.

The turmoil in Athens raised worries that a crisis plan announced by European Union leaders last month could be unwinding.

Under an agreement reached October 27, EU leaders agreed to back a second €100 billion bailout for Greece with the International Monetary Fund. They also negotiated a deal with bondholders to write down the value of Greek debt by 50%.

Sarkozy and German Chancellor Angela Merkel said late Wednesday that Greece will not be able to remain a part of the eurozone if the nation does not abide by the terms of last month's agreements.

In addition, they said Greece will not receive its next installment of bailout money until the uncertainty around the referendum is resolved.

The concern is that Greek voters will reject any plan that would require the government to continue making difficult structural reforms and imposing more austerity measures.

Papandreou said Wednesday that he expects a "positive response" to the planned referendum.

Meanwhile, the finance ministers form the 17 euro area nations were set to meet Thursday to discuss ways to expedite implementation of the other parts of the crisis plan, including new capital requirements for banks and a scheme to leverage a government-backed rescue fund.